The UK should not be “frightened to death” of the trade tariffs that could be introduced after Brexit as they may not prove to be a disaster, the head of the Scottish fishing industry has said.

Bertie Armstrong, chief executive of the Scottish Fisherman’s Federation, told the Commons Brexit select committee that the fishing sector stood to see a doubling or more of its catch when Britain took back control of its waters.

He said the World Trade Organisation tariff on fish was between 5% and 10%, while the pound had dropped by almost 20% against the euro after the EU referendum.

“Let us not be frightened to death of tariffs at all: they may be consumed in the noise of currency fluctuation and some small tariff may not be disaster,” he said.

“We must very much change the rhetoric of ‘we must be in the single market, we must be in the single market.’ We don’t need a single market, we need an adequate market.”

Last week a House of Lords EU committee said fishing communities, who campaigned vigorously for a leave vote, may have unrealistic expectations of reducing foreign fleets operating in British waters.

In Aberdeen on Monday, the Commons committee heard that almost 60% of all fish removed from British waters was removed by other EU countries.

“More than half of our natural resource goes elsewhere – that is unthinkable for another coastal state. Taking that back is not an act of regression, it’s an act of normality,” Armstrong told the committee.

He said the EU common fisheries policy was an act of tremendous generosity by the UK to other countries, and the “monstrous” imbalance had to be redressed.

The Tory MP Michael Gove put it to him that if it was correct that Norway landed three times as much fish as Britain, there was potential for Britain’s catch to “at least double” post Brexit.

“That’s entirely possible,” replied Armstrong.

In an earlier evidence, Prof Michael Keating, a constitutional expert and chair in Scottish politics at the University of Aberdeen, said he found the notion that Scotland could stay in the single market while the rest of the UK exited “extremely difficult”.

Nicola Sturgeon is due to publish detailed proposals on the matter on Tuesday.

“We’ll know tomorrow but the suggestion is that Scotland could stay in the single market if the rest of the UK came out, and I find that extremely difficult to imagine because if you’ve got the rest of the UK out of the single market and Scotland in along Norwegian lines, you would have a single market border between England and Scotland and that would cause problems for trade within the UK,” Keating said.

“It would not only require barriers between Scotland and the rest of the UK but also require the evolution of all single market powers to the Scottish parliament, so we could transpose the European directives.”

He said “technically that could be done” but it was the most complicated of all potential settlements, and one neither the UK or the EU were likely to support.

Deirdre Michie, the chief executive of Oil and Gas UK, told the committee that the key challenge facing her industry was lack of investment, which pre-dated the Brexit vote.

However, she said the uncertainty and unpredictability created by the decision to leave the EU created an additional risk for the industry, and called for the government to offer clarity on a number of issues, including the internal energy market.

“We need to ensure that the government doesn’t get distracted by Brexit,” she said. “We want to stay part of the internal energy market, and it’s very important that we are clear how we are going to manage that, as well as what kind of tariff barriers are imposed.”

Both Michie and the fishing sector witnesses said one of the biggest challenges was the future of migrant workers, who made up significant parts of the workforces in the lower end of the skills ladder in fishing and the higher end in exploration.

“We are a global industry and thrive on the diversity of people and skills. In terms of some specialised skills, sourcing from Europe has been very important, for example sub-sea engineering expertise,” said Michie.

Michael Bates, development officer for the Scottish Seafood Association, said the fishing industry would have to make itself more attractive to local workers if it suddenly found itself without an EU workforce.